The determination of analytes has become very useful in a variety of fields such as biochemical research, environmental and industrial testing, and especially medical diagnostics. The monitoring of therapeutic drug levels and other analytes in biological fluids such as serum, plasma, whole blood, urine, and the like, has become very useful to provide physicians with information to aid in patient management. The monitoring of such drug levels enables adjustment of patient dosage to achieve optimal therapeutic effects, and helps avoid either subtherapeutic or toxic levels.
A test sample may contain one or more detectable compounds having chemical structures which are substantially similar to, or which resemble, or which could resemble, and therefore be indistinguishable from, the desired analyte of interest. For example, in the area of medical diagnostics where it is important to monitor the level of therapeutic drugs, a number of drugs having substantially similar chemical structures may be administered to a patient wherein a test sample from such patient could contain detectable levels thereof.
In such instances, the analytical determination of the desired analyte may be interfered with by the presence of such one or more additional substances having substantially similar chemical structures to the chemical structure of the analyte of interest to thereby produce inconsistent and inaccurate results. In particular, where the analytical determination involves immunoassay techniques employing antibodies capable of binding to the analyte of interest, such antibodies may also bind or crossreact with such other substances having substantially similar chemical structures. Similarly, where the analytical determination involves high pressure liquid chromatography techniques or thin layer chromatography techniques, the elution profile of the analyte of interest may be indistinguishable from the elution profile of such other substances having substantially similar chemical structures.